BIRDS OF NORTH AND MIDDLE AMERICA. 541 



Bill longer than head, large antl stout, the exposed culmen more 

 than one-fifth as long as whig; gonys much shorter than mandibular 

 rami, straight or very nearly so, its basal angle not prominent; 

 depth of bill at base equal to nearly one-fourth the length of com- 

 missure; nostril elliptical, narrower posteriorly, separated from the 

 nearest loral feathering by a space much greater than length of 

 nostril; anterior outline of feathering on head without indentation 

 at base of culmen, where truncated or slightly convex, sloping thence 

 downward and backward to the rictus, sometimes with a very smpll 

 projecting angle (latero-frontal antia) on each side of base of culmen. 

 Wing long and pointed, the longest primary (outermost) exceeding 

 distal secondaries by nearly twice the distance from tips of the latter 

 to bend of wing. Tail much less than half as long as wing, forked 

 for about one-fourth its length, the lateral rectrices rather abruptly 

 contracted, but not acuminate, terminally. Tarsus longer than 

 middle toe without claw (but shorter than middle tow with claw); 

 webs between anterior toes with anterior edge sUghtly incised. 



Plumage and coloration. — -Plumage distinctly blended only on 

 pileum. Adults with pileum, nape and auricular region black (the 

 feathers tipped with white in post-nuptial plumage), the rest of 

 upper parts grayish brown or brownish gray, the distal wing-coverts 

 and under parts white. 



Range. — South America; accidental in Cuba. (Monotypic.) 



PH^TUSA CHLORIPODA (Vieillot). 



LARGE-BILLED TERN. 



Adults in breeding plumage (sexes alike). — Pileum, nape, and 

 auricular region uniform black, this descending to anterior angle of 

 eye and extending along median line of hindneck; back, scapulars, 

 proximal wing-coverts, tertials, rump, upper tail-coverts, and tail 

 plain deep neutral gray ; distal smaller wing-coverts, secondaries, greater 

 wing-coverts, lores (sometimes anterior margin of forehead, narrowly), 

 and under parts immaculate white, the sides and flanks more or less 

 strongly tinged with pale or pallid neutral gray, the sides of neck 

 deeper gray; primary coverts and primaries dull black, the innermost 

 primaries with inner webs more grayish and margined terminally 

 with white; inner webs of primaries with an extensive white "wedge," 

 especially the outermost; bill yellow, more or less tinged with grayish 

 or horn color basally; legs and feet grayish dusky (said to be olive, 

 with yellow webs, in life). 



Adults in post-nuptial plumagel — Similar to breeding adults, but 

 feathers of the black pileum tipped wdth grayish white. 



Immature. — Essentially like adults but pileum light gray, deepen- 

 ing into black on auricular region and near anterior angle of eye; 

 back, etc., pale gray (between light neutral gray and light mouse 



